The surgical treatment of solid tumors frequently involves the resection and post-operative histopathological assessment of sentinel and loco-regional lymph nodes to determine the extent to which the cancer may have spread. This information is also used to stage the disease. The stage of the disease determines the prognosis and dictates treatment strategies. Assessing lymph node status (whether each is normal, reactive, or contains metastatic disease) and staging the disease intraoperatively has significant opportunity to improve the treatment of cancer, and the use of high- resolution real-time intraoperative imaging has the potential to guide interventions, rather than relying solely on post-operative histopathology. This project involves the clinical translation and investigation of intraoperative three-dimensional optical coherence tomography (3-D OCT) for assessing the micro- architecture of lymph nodes. In contrast to all other imaging techniques that either require resection, bisection, and disruption of lymph nodes, or offer insufficient resolution to visualize morphology in situ, 3- D OCT imaging can be performed through the intact capsule of surgically-exposed lymph nodes that can remain in situ. Through preliminary results, we have demonstrated that 3-D OCT can differentiate between normal, reactive, and metastatic lymph nodes based on image biomarkers. The specific aims of this project outline a systematic approach for characterizing image biomarkers in both ex vivo and in situ lymph nodes, and with an intraoperative 3-D OCT system that incorporates an advanced handheld MEMS-scanner-based imaging probe. A novel computational reconstruction algorithm called Interferometric Synthetic Aperture Microscopy (ISAM) is applied to acquired image data to determine if higher spatially-invariant resolution increases the sensitivity and specificity of lymph node status determination. The successful completion of these aims and project will result in a new statistically- validated imaging technology capable of performing image-guided surgical interventions. The intraoperative assessment of lymph node status and the staging of cancer has the potential to update and direct the surgical intervention in real-time, to reduce or eliminate the need for the surgical removal of lymph nodes, to reduce costs, and most importantly, to reduce or eliminate the risks of lymphedema, a highly morbid and lifelong complication from the surgical treatment of many types of cancer. PUBLIC HEALTH RELEVANCE: The intraoperative assessment of lymph nodes during cancer surgery has the potential to reduce patient complications, reduce costs, and provide point-of-care feedback to update the surgical treatment plan. Three-dimensional optical coherence tomography (3-D OCT) can image and assess lymph node status, providing real-time feedback and diagnostic information during surgical interventions.